Method for preparing polyvinyl alcohol fibers employing wet spinning techniques



United States Patent METHOD FOR PREPARING PULYVINYL ALCO- HOL FIBERSEMPLOYING WET SPINNING TECHNIQUES Teruo Suda and Sadamaru Miyazaki,Kurashiki City,

Japan, assignors of one-fourth to Air Reduction Company incorporated,New York, N.Y., a corporation of New York, and three-fourths toKurashiki Rayon Co., 5111., Okayama Prefecture, Japan, a corporation ofapan No Drawing. Filed Apr. 4, 1960, Ser. No. 19,479

Claims priority, application Japan Apr. 7, 1959 11 Claims. (Cl. 18-54)This invention relates to an improved process for the production ofpolyvinyl alcohol fibers or filaments. More particularly, the inventionrelates to an improved wetspinning process for the production ofpolyvinyl alcohol fibers involving extruding a solution of polyvinylalcohol in the formof fine streams into a coagulating liquid to formfilaments.

Wet-spinning techniques for the production of polyvinyl aloohol fibersare known in the art. Generally, fibers produced by such prior wetspinning processes have a kidney-shaped cross-section which is composedof distinct skin and core regions. The prior wet spun polyvinyl alcoholfibers tend to be somewhat opaque and diffieult to dye.

It is an object of invention to provide an improved wet spinning processfor the production of polyvinyl alcohol fibers.

It is a further object to provide for the production by wet spinning ofpolyvinyl alcohol fibers having improved properties, -inoluding improveddyea-bility.

Other objects will be apparent from the following detailed descriptionof the invention.

In accordance with this invention, it has now been found that improvedpolyvinyl alcohol fibers can be wet spun by incorporating sodiumcarboxymethyl cellulose, sodium alginate or gum arabie in the polymericspin ning solution and forming fibers from the additive-containingpolymer solution by conventional wet spinning techniques. As a result ofthe incorporation of the abovementioned additives in the polymerspinning solution, wet spun fibers or filaments are obtained which havea more homogeneous cross-sectional configuration and which have greatlyimproved dyeing properties. Fibers produced by the invention tend to berounder in cross-section and more transparent.

The following tests are illustrative of the invention and show theadvantages obtainable through practice of the instant invention:

Polyvinyl alcohol having an average degree of polym erization of 1700was dissolved in water to form a solution containing 13% by weight ofpolymer. A portion of this solution was taken as blank sample 1, andsodium carboxymethyl cellulose (hereinafter referred to as CMC) wasadded in different amounts to additional quantities of the polymersolution to forms samples 2, 3 and 4, viz. sample 2, 5% CMC; sample 3,CMC; and sample 4, 20%, all percentages being by weight and based on theweight of polyvinyl alcohol in the sample.

The resulting spinning solutions were extruded through a multi-holespinneret of conventional type into a saturated aqueous coagulatingsolution of sodium sulfate at 45 C. to form fibers or filaments.coagulating bath immersion length was 1.5 meters, and the fibers werewithdrawn from the coagnilating bath at a speed of 10 meters/minute. Thefibers were roller stretched 400%. After air drying at 180 C. in ahot-air bath, the filaments were heat-treated in a hot-air bath at 225C.

3,091,509 Patented May 28, 1963 "ice for 30 seconds. Subsequently, thefibers were formalized in an aqueous bath containing, by weight, 5%formaldehyde, 15% sulfuric acid, and 15 sodium sulfate for 1 hour at 70C.

The fibers were then tested to determine strength, elongation shrinkagein boiling water, dye absorption when dyed for 2 hours at C. in a bathcontaining, by weight, 2% Nippon fast violet BB and 10% of sodiumsulfate, the weight ratio of dye bath to fibers being 50:1. Similarly,there was also determined the dyeing concentration or saturation valueK/S after dyeing to the extent of 10 mg./g. in a bath containing varyingconcentrations of Congo red and 10% of sodium sulfate for 2 hours at 80C., the ratio of bath to fibers being 50:1.

The dyeing concentration value K/S equals R being the reflectioncoeflicient at a wave-length of 520. The following table shows theresults obtained:

TABLE I Sample i PPS" cow:

The above results show that, as the amount of CMC is increased up toaround 20%, the dye concentration improved markedly and thedye-absorption similarly improved. An addition of over 30% was foundimpracticable, because the spinning fluid was then diffieult to filter.On the other hand, referring to the effects of CMC concentration on thestrength and elongation of the fiber, it will be seenthat the strengthdropped somewhat as the amount of CMC increased, whereas the elongationdid not substantially change. When the cross-section of these fiberswere examined under the microscope, sample (1) had the usual flat shape,with a transparent exterior layer and an interior layer of granularstructure, but in the case of samples (3) and (4), this uneven structurewas not observed, and the fibers were found to be entirely homogeneousand had a circular crosssection. Sample (2) exhibited an interiorgranular structure to a slight degree but was essentially circular incross-section. In addition, the fibers obtained from spinning solutionscontaining CMC had a soft and smooth feel, and had a tendency to give atactile impression resembling that of an oil-treated fiber. When sodiumsulfate was added along with the CMC, an unevenness was created aroundthe periphery of the cross-section, and the coeflicient of utilizationof spinnability was highly advanced in this case.

When these tests were repeated with spinning solutions containing likequantities of sodium alginate instead of CMC the same results wererealized.

In order to demonstrate the activity of gum arabic as a spinningsolution additive, polyvinyl alcohol having an average degree ofpolymerization of 1700 was dissolved in water to form a solutioncontaining 15% by weight polymer. Commercial gum arabic was added invarying amounts as indicated in the table below to samples of thepolymer solution, one sample being used as a control and containing nogum arabic.

The resulting spinning solution samples were extruded through amulti-hole spinneret into a saturated aqueous coagulating solution ofsodium sulfate at 45 C. to form Sample No erized with the polyvinylalcohol. alcohol with other materials such as amino-acetalized fibers.The coagulating bath immersion length was 1.5 meters, and the fibersleft the coagulating bath at a speed of meters/minute. The fibers wereroller stretched by-300%. After air dryingat 180 C., the fiberswereheated in air at 225 C. for 30 seconds. The fibers were then formalizedin an aqueous bath containing, by weight,'5% formaldehyde, sulfuricacid,-and 15% sodium sulfate at 70 C. for l.hour.

The fibers were then tested for strength,- elongation, shrinkage inboiling water, and dye absorption when dyed for 1 hour at 80 C. in a dyebath containing, by weight, 2% Congo red and 10% sodium sulfate, theweight ratio of dye bath to fibers being 50:1. The dyeing concentrationvalue K/S was also determined after dyeing to the extent of 10 mg./g. ina bath containing varying concentrations of Congo red and 10% sodium.sulfate for 2 hours at 80 C., the ratio of bath to' fibers. being 50:1.

The following table shows the results obtained:

TABLE II ocean None A marked advancement in the concentration of dye wasnoted with the use of up to of gum arabic whereas at concentrations of30% the effect tended to diminish. On the other hand, the effect of thegum arabic on strength and elongation was negligible up to 30%. Whenexamined under the microscope, the cross-,- section of the fibers ofsample (1a) had a fiat and trans parent external layer and an internallayer having a conventional granular structure. In the case of samples(3a), (4a), and (5a), however, this uneven structure was not found but,instead, a transparent and uniform structure was noted. In samples (2a)and (6a) an insignificant internal granular structure was observed. Suchchange in the structure and cross-section of the fibers coincided withthe improvement in dye concentration. The shape of the fibers approacheda true circle in the order of samples from (1a) to (6a), and thefullness of the fibers also showed a similar advancing tendency.

All commercial forms of CMC, sodium alginate and gum arabic are suitablyused in accordance with this invention.

Similarly commercial forms of polyvinyl alcohol are suitable for use butthe polyvinyl alcohol preferably consists of at least about 98% vinylalcohol units. Minor amounts of other monomers can, however, be copolym-Blends of polyvinyl polyvinyl alcohol as described in Osugi et al. US.Patent 2,906,594 can also-be employed.

In carrying out the invention the additive, viz. CMC, sodium alginate,or gum arabic is added to-the spinning solution in an amount sufficientto improve the dyeing properties of filaments prepared therefrom.Generally it is preferred to use at least about 2% of additive based onthe'weight of polyvinyl alcohol polymer, although at least about 5% ofadditive is particularly preferred in the case of CMC and sodiumalginate. Excessive amounts of CMC, sodium alginate or gum arabic whichcause spinning difiiculties or which undesirably alfect other filamentproperties to a significant degree should be avoided. Generally, it ispreferred to use about 2-30% based on the weight of polyvinyl alcoholalthough amounts outside this range can be used.

The amount of polyvinyl alcohol and other polymers,

4 when used, is selected in accordance with conventional procedures.Generally, concentrations of about 15% by weight, e.g. 13-15%, areemployed, but higher or lower concentrations in accordance with knownspinning techniques are fully applicable. 1 In'this connection,reference is made to Cline et al. US. Patent 2,610,360.

The spinning solution containing polyvinyl alcohol and theabove-specified additives can be spun to form filaments or fibers byknown wet spinning methods, as described for example intheabove-mentioned Cline et al. patent and the above-mentioned Osugi et al.patent. A n especially preferred spinning technique is described 1rcopending application Serial No. 336,166 of Tomonari el al. filedFebruary 10, 1953, now US Patent No 2,988,802, dated June 20, 1961.Other wet spinning methods can, however, be used.

After formation of the fibers by wet spinning the fila ments can befurther treated by stretching, heat treating acetalization, and the liketo produce fibers with desir able and outstanding properties, usingknown technique: as described in said patents.

The present invention thus provides. a. simple, conven ient andinexpensive method for producing polyvinyl'al cohol fibers havingimproved dyeing properties by. we spinning techniques. The process ofthe invention over comes dyeing diificultiespeculiar to previous'wetspin ning techniques used in theproduction of polyvinyl al cohol fibers.

' It has 'been found that commercial'soluble"starch. a described incoperiding application Tan'a'be'et al.,ES .N 814,368, filed May 20,1959, now Patent No.'3;044,974 dated July 17, 1962, may-be used'in"combination wit] the above-mentionedadditives, particularly with CMC toprovide further improved dye concentrationiatleast in equal amount ofsuch starch being used and *pr'eferabl about 2 /2 times the-quantity ofCMC' or otheradditiv of this invention.

The invention will be further understood from the' fol lowing specificexamples of practicalapplication. Ho t ever, it will be understood that'these examples' are nc to be construed as limiting the scope ofthe'presentir vention in any'manner. In these examples;all-parts at byweight.

Example 1 section was homogeneous and circular in shape, and

exhibited substantially better dyeing characteristics the the fiber usedas control which was spun from a solutic containing no CMC.

Example 2 Wet-spinning was effected with a water solution e01 taining12% -of polyvinyl alcohol having an averag degree of polymerization 2000and CMC '(10%'bas on the polyvinyl alcohol) in a saturated watersoluti'c of sodium sulfate at 45 C. The fiber was subjectedroller-stretching by 400%, continuously dried in a he air bath at C.,and then heat-treated-in super-heat steam under 1 atmosphere pressure at210 C. for minutes. The fiber was then benzalized in a water s'ol tioncontaining benzaldehyde (1%), sodium dibuty naphthalene-sulfonate(0.3%), sulfuric acid (2%) 60 C. for one hour. The fiber was homogenous,ax round in cross-sectional, shape whereas the control h: an unevenstructure. When tested with cellitone fa blue FFR, the former fiber dyedto a far deeper shat than the latter control fiber.

Example 3 A water solution containing 14% of polyvinyl alcohol of anaverage degree of polymerization of 1700 and CMC (8% based on thepolyvinyl alcohol) and soluble starch (20% based on the polyvinylalcohol) was subjected to wet-spinning in a saturated water solution ofsodium sulfate at 50 C., then roller-stretched by 400%, and continuouslydried. The fiber was then heat-treated in a hot air bath of 225 C. for30 sec., and was formalized in a water solution containing formaldehydesodium sulfate (15%) and sulfuric acid (15%) at 60 C. for one hour. Thefiber was transparent and homogeneous, and its cross-section wascircular, having a soft and smooth feel. The dyeing characteristics weresubstantially better than in the control to which CMC and soluble starchwere not added.

Example 4 Wet-spinning was effected with a water solution containing 13%of polyvinyl alcohol of an average degree of polymerization of 1500 andCMC (5% based on the polyvinyl alcohol) and sodium sulfate (15% based onthe polyvinyl alcohol) in a saturated water solution of sodium sulfateat 45 C. Spinning was followed by roller-stretching by 400% andcontinuous drying by heating. The fiber was then heat-treated in asaturated water solution of sodium sulfate at 120 C., and formalizedwith a water solution of formaldehyde (5% sodium sulfate (15%) andsulfuric acid (15%). The fiber has a cross-section with high degree offullness and with only slight unevenness along the periphery of thecross section. Compared with the control which involved no addition ofCMC and sodium sulfate, it showed a much better dyeing action.

Example 5 A water solution of 13% of polyvinyl alcohol of a degree ofpolymerization grade of 1600 and sodium alginate based on the polyvinylalcohol) was subjected to wet-spinning in a saturated water solution ofsodium sulfate at 50 C., and heat-treating in a saturated water solutionof sodium sulfate at 125 C. for 2 hours. The fiber was then acetalizedin a water solution containing formaldehyde (5%), fl-cyclohexylaminobutylaldehyde (2%), sulfuric acid (15%), and sodium sulfate (10%), at 60C. for 2 hours. This fiber had a homogeneous and circular cross section,and the dye concentration was significantly higher when compared withfiber from a control to which no sodium alignate was added in tests withan acid dye (acid brilliant scarlet 3R) (2%), and sulfuric acid (1%),with dye bath ratio of 50:1, at 80 C., for one hour.

Example 6 A water solution was prepared by adding to water a polyvinylalcohol of a degree polymerization of 1600 and an amino-acetalizedpolyvinyl alcohol which was acetalized by means ofB-cyclohexylaminobutyl aldehyde. The quantities of the polyvinyl alcoholand amino-acetalized polyvinyl alcohol were selected to provide asolution of an average percentage of aminoacetalation of 1% and a totalconcentration of polyvinyl alcohol component of 15%. To this solutionwas added CMC in the amount of 10% based on the polyvinyl alcoholcomponent present. This water solution was wet-spun in a saturatedaqueous solution of sodium sulfate at C., and after roller-stretching by200%, it was dried by means of hot-air.

This fiber was stretched by 200% in hot air at 225 C., and was thenheat-treated at 230 C. at constant yarn length. Benzalization waseffected in a water solution of benzaldehyde (2%), methanol (40%), andsulfuric acid (10%) at C. for one hour. The fiber was homogeneous andhad a round cross-section. Compared with the control to which no CMC wasadded, it attained a transparent skin layer.

6 substantially greater concentration of dye when tested with acidbrilliant scarlet 3R (2%), acetic acid (1%), with a dye bath ratio of50:1, at C. for one hour. Both fibers absorbed the dye in the dyeingbath completely.

Example 7 A 20% water solution of polyvinyl alcohol of an average degreeof polymerization grade of 1000, containing gum arabic (9% based on thepolyvinyl alcohol), was subjected to wet-spinning at 50 C. in an aqueoussolution containing sodium sulfate (410 g./l.), and the fiber obtainedwas dried. After heat-treatment in hot air at 220 C. for one minute, thefiber was formalized in a water solution containing formaldehyde (4%)and sulfuric acid (15%) at 60 C. for 2 hours. This fiber had goodresistance to boiling water, its cross section was more homogeneous andtransparent than that from con trol (with no addition of gum arabic)which was opaque, and in which a granular structure was noted inside aWhen tested with Nippon fast violet BB the former fiber exhibited a muchhigher concentration of dye than the control fiber.

Example 8 A water solution containing 15% of polyvinyl alcohol of anaverage degree of polymerization of 1700 and gum arabic (10% based onthe polyvinyl alcohol) was wetspun in a saturated sodium sulfate watersolution at 45 C., was subjected to roller-stretching by 400%, and wascontinuously dried in hot air at 180 C.

This fiber was heat-treated in super-heated steam at 1 atmospherepressure at 210 C. for 2 min, and was benzalized in a water solutioncontaining benzaldehyde (1%), sodium dibutylnaphthalenesulfonate (0.3%),and sulfuric acid (2%) at 60 C. for one hour. The fiber had atransparent and uniform cross-section. On the other hand, the controlfiber formed from a solution to which no gum arabic was added was opaqueanduneven in its crosssection. When tested with cellitone fast blue FFR,the former fiber was dyed to a far deeper color than the latter.

Example 9 A 14% water solution of polyvinyl alcohol with an averagedegree of polymerization grade of 1600, and gum arabic (13% againstpolyvinyl alcohol) was wet-spun in an aqueous solution saturated withsodium sulfate at 50 C., and the fiber was air dried. This fiber washot- =stretched by 700% in hot air at 230 C., and shrunk by 15% in airat a temperature of 235 C. Acetalization of the fiber was then effectedby means of an aqueous solu tion containing formaldehyde (0.5%fl-cyclohexylaminobutylaldehyde (2% sulfuric acid (15%) and sodiumsulfate (10%) at 60 C. for 2 hours. Compared with the control fiber,which involved no addition of gum arabic, a much higher colorconcentration was achieved when the fiber was dyed with acid scarlet 3R(acid dye) (2% sulfuric acid (1% with a dye bath ratio 50:1, at 80 C.for one hour.

Example 10 A water solution was prepared by adding to water a polyvinylalcohol of an average degree of polymerization grade of 1700 and theaminoacetalized polyvinyl alco hol which had been 30% acetalized bymeans of fl-cyclohexylaminobutylaldehyde. The quantities of the twopolyvinyl alcohols were selected to provide in the solution an averagepercentage acetalization of 1%, and a total polyvinyl alcohol componentconcentration of 15 To this solution gum arabic (9% of polyvinyl alcoholcomponent) was added. The solution was then subjected to wet-spinning ina saturated aqueous solution of sodium sulfate at 45 C. and the fiberwas rollerstretched by 200% and then dried in hot air. The fiber wasfurther stretched in hot air of 225 C- by 200%,

' known techniques.

and heat-treated at 230'fC. =at constant yarn length.

Benzalization was then iafiect'ed by means of a water solution ofbenzaldehyde (2%), methanol (40%),and sulfuric acid at 60l C; for-onehour. As compared with the control fiber which involved no gurm arabic,

spun in a saturated aqueous solution of-sodium sulfate at 50- C. Thefiber was wet-heat-treated in a saturated sodium sulfate bath at 120 C.for 2 hours, and formalized in usual manner. This fiber showcd'muchbctter-dyeing characteristics than the control fiber'which was formedwithout use of gum arabic and had a transparent appear- Example 12 Awater solution containing 13% of polyvinyl alcohol with an averagedegreeof polymerization of 2000 and.

gum arabic (15% based on polyvinyl alcoholiwaswetspun in a saturatedaqueous solution "of sodium" sulfate a-t75 C. The fiber was heat-treated-in at 230 C. with constant yarn length audit was then formalized in anaqueous solution of formaldehyde 5% ),s'1ilfu'n'c acid and sodiumsulfate (5%) at 65 C; forione" hour.

As compared with the control fiber which was produced without use of gumar'abic, the former fiber had a much rounder cross-section, beingsubstantially a circular'form.

Ithad a transparent appearance and alhi'gh dye concentration when dyed.

'Example 13 Wet-spinning was etfected with a water solution con-.taining 13% of polyvinyl alcohol havingan average degree ofpolymerization grade of 1700 and-gum arabic (10% based on the polyvinylalchol) and a bluepigment (1% based on the polyvinyl alcohol) in asaturated aqueous-solution of sodium sulfate at 45 C., and the fiberproduced was heat-treated in hot air at 220 C.

The fiber was then formalized in an aqueous solution containingformaldehyde (5%), sulfuric acid (15% and sodium sulfate (15%) at 70 C.for one hour. The fiber could be dyed to a remarkably high concentrationof dye, and had much brighter hue as compared with .the-

control fiber formed without gum arabic.

It will be understood that, unless otherwise indicated, conventionalwet-spinning operations are employed in -producing the fiber-s andsubsequent heat treatment,

stretching and relaxation are effected iii-accordance with Similarly,conventionalapparatus is employed in carrying out the process of thisinvention including conventional mixing and emulsifying units, spinningdevices and fiber treating apparatus. ditions and the relativerelationships set forth in the examples are those preferred in carryingout the process of the invention but it will be understood that otherconditions and relationships :may be used within'the scope of theinvention, 'Similarly, conventional dyeing tech- The conniques andapparatusizare suitably employed upon the .fibers produced by the.process of this invention.

It will also be under-'st'ciod that various changes and modificationsin' addition to those indicated above may be made in the embodimentsherein described without departing from the scope ofthe invention asdefined in the appended claims. 'It' is intendedftherefore, that allmatter contained in the foregoing description shall be interpreted asillustrative-only and not as limit-ative of the invention.

We claim:

1. The method of preparing polyvinyl alcoholfibers whichcomprises-forming an aqueous polyvinyl alcohol spinning solutioncontaining polyvinyl alcohol in an amount suitable for wet spinningoffibers and containing an additive selected from the group consistingof sodium carboxymethyl cellulose, sodium alginate and gum arabic in theamount of 2 to 30%' by=wei-ght based on the weight of the polyvinylalcohol in said solution and sufiicient to improve the dyeing propertiesof fibers formed fromsaid solution, and wet-spinning said solutioninto.a coagulating liquid efiecti ve-to coagulate :said polyvinyl-alcohol insaid solution to form fibers.

2. The method-of.- claim I, wherein .saidv additive is sodiumcarboxymethyl. cellulose.

3. The method of claim .1, wherein. .said additiveis sodium: alginate.

4. The-method-ofuclaim1, wherein saidadditive is gum arabic. q

- 5.-The method 'of. claim 1,;wherein said. coagulating .liquid isan=aqueous sodium sulfate solution.

- 6. The method of claim 1,-wherein said polyvinyl alco- -hol is presentin said aqueous solution in an amount up to about 20% by weight.

7. The method of preparing polyvinyl alcohol fibers having improveddyeabilityiir'liich comprises forming an aqueous polyvinyl:aleoholspinning solution= containing about 15% byweight of polyviny-lalcohol' and containing 2 to 30% by weightbased-on theweight'oft-saidpolyvinyl alcohol in said solution of an additiveselected-from the group consistingof sodium 'carboxymethylr-wcellulose,sodium alginate randz, anabic, said -a.mount\-ofsaid additive:beingsuflicient toimprove the dyeingproperties offibersformed fronrsaidsolution, "and wet spinning said solution to form fibers.

'8JThe method of claim- 7, whereinsaid'additive is sodium carboxymethylcellulose.

' 9. The method of claim 7,-wherein said additive is -'-sodium alginate.

10. The. method of claim 7, wherein said-- additive .is gum arabic.

11. The method of claim 7, wherein said wetzspinning is effected byintroducing saidsolution into an aqueous sodium sulfate solution.

References fiitedinathe'file of-this patent UNITED-STATES PATENTS2,092,512 Hermann et a1 Sept. 7, 1937 2,146,295 Hermann et a1. Feb. 7,1939 2,364,738 Marberg et a1 Dec. 12, 1944 2,524,008 Deney Sept. 26,1950 2,716,049 Latour Aug. 23, 1955 2,764,568 Hawkins Sept. 25, 19562,906,594- Osu'gi et a1. Sept/29, 1959

1. THE METHOD OF PREPARING POLYVINYL ALCOHOL FIBERS WHICH COMPRISINGFORMING AN AQUEOUS POLYVINYL ALCOHOL SPINNING SOLUTION CONTAININGPOLYVINYL ALCOHOL IN AN AMOUNT SUITABLE FOR WET SPINNING OF FIBERS ANDCONTAINING AN ADDITIVE SELECTED FROM THE GROUP CONSISTING OF SODIUMCARBOXYMETHYL CELLULOSE, SODIUM ALGINATE AND GUM ARABIC IN THE AMOUNT OF2 TO 30% BY WEIGHT BASED ON THE WEIGHT OF THE POLYVINYL ALCOHOL IN SAIDSOLUTION AND SUFFICIENT TO IMPROVE THE DYEING PROPERTIES OF FIBERSFORMED FROM SAID SOLUTION, AND WET SPINNING SAID SOLUTION INTO ACOAGULATING LIQUID EFFECTIVE TO COAGULATE SAID POLYVINYL ALCOHOL IN SAIDSOLUTION TO FORM FIBERS.
 5. THE METHOD OF CLAIM 1, WHEREIN SAIDCOAGULATING LIQUID IS AN AQUEOUS SODIUM SULFATE SOLUTION.